An ultra-fine cement-based composite cementing material for underground mine filling and its preparation method

Abstract

This application relates to the field of cementitious materials, and particularly to an ultra-fine cement-based composite cementitious material for underground mine filling and its preparation method. The ultra-fine cement-based composite cementitious material for underground mine filling, in parts by mass, comprises the following raw materials: 50-70 parts of ultra-fine cement, 20-30 parts of tailings sand, 10-15 parts of modified desulfurized gypsum, 5-12 parts of fly ash, 8-16 parts of modified resin, 0.5-1.5 parts of reinforcing agent, 0.4-1.2 parts of water reducing agent, 5-15 parts of fiber material, and 40-60 parts of water. The ultra-fine cement-based composite cementitious material prepared in this application not only has excellent mechanical strength and a low shrinkage rate, but also can ensure good water resistance and impermeability performance, thus effectively meeting the diverse performance requirements of the existing mining industry for mine filling materials, expanding the application environment of the ultra-fine cement-based composite cementitious material, and having a very excellent application prospect.

Description

Technical Field

[0001] This application relates to the field of cementitious materials, and particularly to an ultra-fine cement-based composite cementitious material for underground mine filling and a preparation method thereof. Background Art

[0002] With the development of the mining industry, mine filling technology has become one of the important means to solve the ground pressure control and environmental protection of underground goafs. Traditional filling materials are mostly made of ordinary cement and tailings sand. Although they can meet the filling requirements to a certain extent, there are problems such as low early strength, large shrinkage, and high cost. In recent years, in order to overcome these problems, researchers have begun to explore the use of ultra-fine cement-based composite cementitious materials. By mixing ultra-fine cement with other auxiliary materials (such as slag powder, steel slag, industrial by-product gypsum, etc.), these materials not only improve the early strength and stability of the filling body, but also effectively reduce the material cost.

[0003] Although the performance of ultra-fine cement-based composite cementitious materials has been improved, the existing technology still faces the following problems. For example, the problem of insufficient early strength. Under certain geological conditions, the filling body needs to quickly reach a certain strength to ensure the safe production of the mine, while the existing ultra-fine cement-based composite cementitious materials still need to be improved in terms of early strength; high shrinkage rate, and the filling body is prone to shrinkage cracks during the hardening process, affecting its long-term stability and service life; poor waterproof performance, and it is prone to cracks, breakage, and water seepage in a long-term humid environment.

[0004] Therefore, in order to effectively solve the above problems, this application provides an ultra-fine cement-based composite cementitious material for underground mine filling and a preparation method thereof. The ultra-fine cement-based composite cementitious material prepared in this application not only has excellent mechanical strength and low shrinkage rate, but also can ensure good water resistance and impermeability, thus effectively meeting the diverse performance requirements of existing mining industries for mine filling materials, expanding the application environment of ultra-fine cement-based composite cementitious materials, and having very excellent application prospects. Summary of the Invention

[0005] To solve the above problems, in the first aspect of this application, an ultra-fine cement-based composite cementitious material for underground mine filling is provided. Calculated by mass, the raw materials are: 50 - 70 parts of ultra-fine cement, 20 - 30 parts of tailings sand, 10 - 15 parts of modified desulfurized gypsum, 5 - 12 parts of fly ash, 8 - 16 parts of modified resin, 0.5 - 1.5 parts of reinforcing agent, 0.4 - 1.2 parts of water reducing agent, 5 - 15 parts of fiber material, and 40 - 60 parts of water.

[0006] As a preferred scheme, the mass ratio of the ultra-fine cement, tailings sand, fly ash, and fiber material is (55 - 65):(22 - 26):(8 - 12):(6 - 12).

[0007] As a preferred solution, the mass ratio of the ultra-fine cement, tailings sand, fly ash and fiber material is (58-64):(24-25):(8-10):(6-8).

[0008] As a preferred solution, the mass ratio of the ultra-fine cement, modified desulfurized gypsum and modified resin is (55-65):(11-14):(10-15).

[0009] As a preferred solution, the mass ratio of the ultra-fine cement, modified desulfurized gypsum and modified resin is (58-64):(12-13):(12-14).

[0010] As a preferred solution, the average particle size of the ultra-fine cement is 5-15 μm.

[0011] As a preferred solution, the average particle size of the ultra-fine cement is 6-10 μm.

[0012] As a preferred solution, the average particle size of the tailings sand is 0.5-1.5 mm.

[0013] As a preferred solution, the average particle size of the tailings sand is 0.8-1.2 mm.

[0014] As a preferred solution, the fly ash is Class I fly ash or Class II fly ash.

[0015] As a preferred solution, the preparation method of the modified desulfurized gypsum includes the following steps: S1: Add desulfurized gypsum into deionized water, and add titanate coupling agent and polyvinyl alcohol and stir to mix evenly; S2: Add ammonia water, branched starch and silica sol into the reaction solution, heat up to 70-75 °C, and keep the temperature for reaction for 2-2.5 h; S3: After the reaction is completed, add urea into the reaction solution and continuously stir for 100-120 min; S4: After stirring is completed, filter the product and place it in a ventilated oven to dry at 80-90 °C and keep warm for 2-3 h, and it is obtained after completion.

[0016] As a preferred solution, the mass ratio of the desulfurized gypsum, titanate coupling agent and polyvinyl alcohol is (8-10):(0.5-1):(1.6-2.2).

[0017] As a preferred solution, the mass ratio of the desulfurized gypsum, branched starch and silica sol is (8-10):(1-1.4):(0.5-0.8).

[0018] As a preferred solution, the addition amount of urea is 2.5-5 wt% of the total mass of the reaction solution.

[0019] In this application, by adding the above-mentioned modified desulfurized gypsum, the mechanical strength of the composite cementitious material can be effectively improved, the shrinkage rate can be reduced, and its good waterproof performance can be effectively maintained. The added modified desulfurized gypsum can form an active coating layer in the system through the surface action of amylopectin and silica sol on the surface of gypsum particles. The existence of this coating layer can further strengthen the connection inside the cementitious material through the action of surface active groups. Especially, the interaction with the modified resin can form a stable three-dimensional network structure inside during the curing of the composite cementitious material through the multi-branched connection of amylopectin, thus greatly enhancing the compactness between ultra-fine cement particles, further greatly improving the barrier effect of the composite cementitious material on water molecules, reducing the penetration of water molecules in a humid environment, and the formed three-dimensional network structure can strengthen the stability of solid particles in the cementitious material, thus playing an excellent supporting effect and having a good impedance force during shrinkage, thereby ensuring the various properties of the composite cementitious material.

[0020] As a preferred solution, the preparation method of the modified resin includes the following steps: S1: Add acrylonitrile, glycidyl acrylate, and methyl methacrylate to an acryloyl chloride solution, introduce nitrogen, add potassium persulfate, and heat to 80-90 °C for a reaction to generate a prepolymer; S2: Mix the prepolymer with acrylamide, deionized water, and potassium persulfate, fully displace the gas in the reaction system with nitrogen, and react for 6-8 h to obtain a modified product solution; S3: Add ammonia water to the modified product solution to adjust the pH to 8-8.5, and naturally cool down. Then add acetone for cyclic washing 2-3 times and dry to obtain the product.

[0021] As a preferred solution, the mass ratio of acrylonitrile, glycidyl acrylate, and methyl methacrylate is (6-8):(1-1.5):(2-3).

[0022] As a preferred solution, the mass ratio of the prepolymer to acrylamide is (10-15):(35-40).

[0023] The above-mentioned modified resin added in this application can assist in forming a good interfacial film structure inside the composite cementitious material. The existence of this structure can effectively form a blocking force for water molecules inside the composite cementitious material, thereby greatly reducing the penetration and free velocity of water molecules. And the existence of the interfacial film can limit the excessive free movement and shrinkage of particles inside the cementitious material to a certain extent, forming a certain supporting force, thereby improving the overall stability of the internal system of the cementitious material and providing better and stable strength during use.

[0024] As a preferred solution, the reinforcing agent is a composition of triethanolamine and calcium chloride.

[0025] As a preferred solution, the mass ratio of triethanolamine to calcium chloride is (1.5 - 2) : (2.5 - 3.5).

[0026] As a preferred solution, the water reducing agent is at least one of polycarboxylate water reducing agents.

[0027] As a preferred solution, the fiber material is at least one of carbon fiber, glass fiber, polypropylene fiber, nylon fiber, and stainless steel fiber.

[0028] As a preferred solution, the fiber material is glass fiber.

[0029] As a preferred solution, the glass fiber is chopped fiber, with an average diameter of 10 - 15 μm and an average length of 6 - 12 mm.

[0030] The second aspect of the present application provides a preparation method for the above - mentioned ultra - fine cement - based composite cementing material for underground mine filling, specifically including the following steps: S1: Weigh ultra - fine cement, tailings sand, modified desulfurized gypsum, fly ash, and modified resin in proportion, add them to a mixer for dry mixing, and the mixing time is 3 - 5 min to ensure uniform distribution of each component to obtain a dry - mixed material; S2: Mix the enhancer, water reducing agent, fiber material, and water evenly to obtain a mixed solution, and mix the dry - mixed material and the mixed solution until the slurry is uniform and free of lumps; S3: Carry out filling and curing on the obtained slurry, and the curing time is 28 days, and then it is obtained after completion.

[0031] The beneficial effects of the present application are:

[0032] 1. The ultra - fine cement - based composite cementing material for underground mine filling provided in the present application not only has excellent mechanical strength and a low shrinkage rate, but also can ensure good water - resistant and impermeable performance, thus effectively meeting the diverse performance requirements of the existing mining industry for mine filling materials, expanding the application environment of the ultra - fine cement - based composite cementing material, and having a very excellent application prospect.

[0033] 2. A superfine cement-based composite binder material for underground mine filling provided in this application. The addition of modified desulfurized gypsum can effectively improve the mechanical strength of the composite binder material, reduce the shrinkage rate, and effectively maintain its good waterproof performance. The added modified desulfurized gypsum can form an active coating layer in the system through the surface action of amylopectin and silica sol on the surface of gypsum particles. The existence of this coating layer can further strengthen the connection inside the binder material through the action of surface active groups. Especially, the interaction with the modified resin can form a stable three-dimensional network structure inside during the curing of the composite binder material through the multi-branched connection of amylopectin, thus greatly enhancing the compactness between superfine cement particles, and further greatly improving the barrier effect of the composite binder material on water molecules, so as to reduce the penetration of water molecules in a humid environment, and thus obtain good waterproof, anti-shrinkage and strength properties.

[0034] 3. A superfine cement-based composite binder material for underground mine filling provided in this application. The added modified resin can assist in forming a good interfacial film structure inside the composite binder material. The existence of this structure can effectively form a water molecule blocking force inside the composite binder material, thereby greatly reducing the penetration and free velocity of water molecules. And the existence of the interfacial film can limit the excessive free and shrinkage of particles inside the binder material to a certain extent, forming a certain supporting force, and further improving the overall stability of the internal system of the binder material, so as to provide better and stable strength during use. Detailed implementation mode

[0035] The following will further illustrate and demonstrate the technical solutions in the above-mentioned invention content of this application in the form of specific implementation examples. And the following examples are only actual examples for explaining and interpreting the content of the technical solutions in the specification, and should not limit the scope of the claims to be protected by this application. All technical products based on the technical solutions described in the invention content of this application should be covered within the scope to be protected by this application.

[0036] In the following examples, unless otherwise specified, the raw materials are commercially available products that can be obtained, or can be prepared by methods well-known to those skilled in the art.

[0037] Example 1

[0038] Example 1 provides a superfine cement-based composite binder material for underground mine filling. In terms of parts by mass, the raw materials are: 62 parts of superfine cement, 24.5 parts of tailings sand, 12.5 parts of modified desulfurized gypsum, 9.5 parts of fly ash, 14 parts of modified resin, 1.2 parts of enhancer, 0.5 part of water reducer, 7.5 parts of fiber material, and 50 parts of water.

[0039] The average particle size of the ultra-fine cement is 8.5 μm, and it is purchased from the corresponding particle size product sold by Shanghai Kehong New Building Materials Co., Ltd.

[0040] The average particle size of the tailings sand is 0.8 mm.

[0041] The fly ash is Class I fly ash.

[0042] The preparation method of the modified desulfurized gypsum includes the following steps: S1: Add 9.6 parts of desulfurized gypsum to 180 parts of deionized water, add 0.8 part of triisostearoyl titanate isopropyl ester and 1.8 parts of polyvinyl alcohol, and stir and mix evenly; S2: Add 1 part of ammonia water, 1.3 parts of amylopectin and 0.6 part of silica sol to the reaction solution, heat up to 72 °C, and keep the reaction for 2 h; S3: After the reaction is completed, add urea (3.5 wt% of the total mass of the reaction solution) to the reaction solution, and continuously stir for 110 min; S4: After stirring is completed, filter the product and place it in a ventilated oven at 85 °C for drying and heat preservation for 3 h, and it is obtained after completion.

[0043] The desulfurized gypsum is purchased from the industrial-grade desulfurized gypsum product sold by Beijing Yiwei New Materials Technology Co., Ltd.

[0044] The polyvinyl alcohol is PVA2488.

[0045] The amylopectin is purchased from Wuhan Lana White Pharmaceutical Chemical Co., Ltd., and its amylopectin content is ≥75%.

[0046] The silica sol is purchased from the industrial-grade silica sol product sold by Sichuan Muir Chemical Technology Co., Ltd.

[0047] The preparation method of the modified resin includes the following steps: S1: Add 7.5 parts of acrylonitrile, 1.2 parts of glycidyl acrylate and 2.5 parts of methyl methacrylate to 60 parts of acryloyl chloride solution, introduce nitrogen, add 0.12 part of potassium persulfate, and heat up to 85 °C for heating reaction to generate a prepolymer; S2: Mix 12.5 parts of the prepolymer, 38.5 parts of acrylamide, 200 parts of deionized water and 0.22 part of potassium persulfate, and after fully replacing the gas in the reaction system with nitrogen, react for 7.5 h to obtain a modified product solution; S3: Add ammonia water to the modified product solution to adjust the pH to 8.5, and naturally cool down, then add acetone and wash it 3 times in a cycle, and dry it to obtain.

[0048] The intensifier is a composition of triethanolamine and calcium chloride, and the mass ratio of the two is 1.8:3.

[0049] The water reducer is a polycarboxylate water reducer, purchased from the high-performance polycarboxylate water reducer sold by Jinan Yanglan New Materials Technology Co., Ltd., and the water reduction rate is 40%.

[0050] The fiber material is chopped glass fiber with an average diameter of 12 μm and an average length of 8 mm, purchased from the corresponding size products sold by Wanqing Chemical Technology Co., Ltd.

[0051] In the second aspect of this embodiment, a preparation method of the above-mentioned ultra-fine cement-based composite cementing material for underground mine filling is provided, which specifically includes the following steps: S1: Weigh ultra-fine cement, tailings sand, modified desulfurized gypsum, fly ash and modified resin in proportion, and add them to a mixer for dry mixing. The mixing time is 4 min to ensure uniform distribution of each component, and a dry mixture is obtained; S2: Mix the reinforcing agent, water reducing agent, fiber material and water evenly to obtain a mixed solution, and mix and stir the dry mixture and the mixed solution until the slurry is uniform and free of lumps; S3: Carry out filling and curing on the obtained slurry for 28 days, and it is obtained after completion.

[0052] Example 2

[0053] In the first aspect of Example 2, an ultra-fine cement-based composite cementing material for underground mine filling is provided. By mass, the raw materials are: 56 parts of ultra-fine cement, 26 parts of tailings sand, 14 parts of modified desulfurized gypsum, 8 parts of fly ash, 10 parts of modified resin, 1.2 parts of reinforcing agent, 0.5 parts of water reducing agent, 11 parts of fiber material, and 50 parts of water.

[0054] The average particle size of the ultra-fine cement is 8.5 μm, purchased from the corresponding particle size products sold by Shanghai Kehong New Building Materials Co., Ltd.

[0055] The average particle size of the tailings sand is 0.8 mm.

[0056] The fly ash is Class I fly ash.

[0057] The preparation method of the modified desulfurized gypsum includes the following steps: S1: Add 9.6 parts of desulfurized gypsum to 180 parts of deionized water, and add 0.8 part of triisostearoyl titanate and 1.8 parts of polyvinyl alcohol and stir and mix evenly; S2: Add 1 part of ammonia water, 1.3 parts of amylopectin and 0.6 part of silica sol to the reaction solution, heat up to 72 °C, and keep the reaction for 2 h; S3: After the reaction is completed, add urea (3.5 wt% of the total mass of the reaction solution) to the reaction solution and continuously stir for 110 min; S4: After stirring is completed, filter the product and place it in a ventilated oven at 85 °C for drying and heat preservation for 3 h, and it is obtained after completion.

[0058] The desulfurized gypsum is purchased from the industrial-grade desulfurized gypsum products sold by Beijing Yiwei New Materials Technology Co., Ltd.

[0059] The polyvinyl alcohol is PVA2488.

[0060] The amylopectin is purchased from Wuhan Lana White Pharmaceutical and Chemical Co., Ltd., and its amylopectin content is ≥75%.

[0061] The silica sol was purchased from the industrial-grade silica sol product sold by Sichuan Mu'er Chemical Technology Co., Ltd.

[0062] The preparation method of the modified resin comprises the following steps: S1: Add 7.5 parts of acrylonitrile, 1.2 parts of glycidyl acrylate and 2.5 parts of methyl methacrylate into 60 parts of acryloyl chloride solution, introduce nitrogen, add 0.12 parts of potassium persulfate, and heat up to 85 °C for heating reaction to generate a prepolymer; S2: Mix 12.5 parts of the prepolymer, 38.5 parts of acrylamide, 200 parts of deionized water and 0.22 parts of potassium persulfate, and after fully displacing the gas in the reaction system with nitrogen, react for 7.5 h to obtain a modified product solution; S3: Add ammonia water to the modified product solution to adjust the pH to 8.5, and naturally cool down, then add acetone for cyclic washing 3 times, and dry to obtain.

[0063] The reinforcing agent is a composition of triethanolamine and calcium chloride, and the mass ratio of the two is 1.8:3.

[0064] The water reducing agent is a polycarboxylate water reducing agent, purchased from the high-performance polycarboxylate water reducing agent sold by Jinan Yanglan New Material Technology Co., Ltd., and the water reducing rate is 40%.

[0065] The fiber material is chopped glass fiber, with an average diameter of 12 μm and an average length of 8 mm, purchased from the corresponding size product sold by Wanqing Chemical Technology Co., Ltd.

[0066] The second aspect of this embodiment provides a preparation method of the above-mentioned ultra-fine cement-based composite cementing material for underground mine filling, which specifically comprises the following steps: S1: Weigh ultra-fine cement, tailings sand, modified desulfurized gypsum, fly ash and modified resin in proportion, add them into a mixer for dry mixing, and the mixing time is 4 min to ensure uniform distribution of each component to obtain a dry mixture; S2: Mix the reinforcing agent, water reducing agent, fiber material and water evenly to obtain a mixed solution, and mix and stir the dry mixture and the mixed solution until the slurry is uniform and free of lumps; S3: Carry out filling and curing on the obtained slurry, and the curing time is 28 days, and it is obtained after completion.

[0067] Comparative Example 1

[0068] The specific implementation manner of this comparative example is basically the same as that of Example 1, the difference is only that: for the ultra-fine cement-based composite cementing material for underground mine filling, by mass, the raw materials are: 80 parts of ultra-fine cement, 20 parts of tailings sand, 6.5 parts of modified desulfurized gypsum, 9.5 parts of fly ash, 22 parts of modified resin, 1.2 parts of reinforcing agent, 0.5 parts of water reducing agent, 7.5 parts of fiber material, and 50 parts of water.

[0069] Comparative Example 2

[0070] The specific implementation manner of this comparative example is basically the same as that of Example 1, except that: for the ultra-fine cement-based composite cementing material used in underground mine filling, by mass, the raw materials are: 70 parts of ultra-fine cement, 24.5 parts of tailings sand, 18.5 parts of modified desulfurized gypsum, 9.5 parts of fly ash, 5.5 parts of modified resin, 1.2 parts of reinforcing agent, 0.5 part of water-reducing agent, 7.5 parts of fiber material, and 50 parts of water.

[0071] Comparative Example 3

[0072] The specific implementation manner of this comparative example is basically the same as that of Example 1, except that: the preparation method of the modified desulfurized gypsum includes the following steps: S1: Add 18.5 parts of desulfurized gypsum to 280 parts of deionized water, and add 0.6 part of triisostearoyl titanate and 1.2 parts of polyvinyl alcohol and stir to mix evenly; S2: Add 2.2 parts of ammonia water, 1.3 parts of branched starch and 0.6 part of silica sol to the reaction solution, heat up to 72 °C, and keep the reaction for 2 h; S3: After the reaction is completed, add urea (3.5 wt% of the total mass of the reaction solution) to the reaction solution, and continuously stir for 110 min; S4: After stirring is completed, filter the product and place it in a ventilated oven at 85 °C for drying and heat preservation for 3 h, and it is obtained after completion.

[0073] Comparative Example 4

[0074] The specific implementation manner of this comparative example is basically the same as that of Example 1, except that: the preparation method of the modified desulfurized gypsum includes the following steps: S1: Add 9.6 parts of desulfurized gypsum to 180 parts of deionized water, and add 0.8 part of triisostearoyl titanate and 1.8 parts of polyvinyl alcohol and stir to mix evenly; S2: Add 1.2 parts of ammonia water, 0.5 part of branched starch and 3 parts of silica sol to the reaction solution, heat up to 72 °C, and keep the reaction for 2 h; S3: After the reaction is completed, add urea (3.5 wt% of the total mass of the reaction solution) to the reaction solution, and continuously stir for 110 min; S4: After stirring is completed, filter the product and place it in a ventilated oven at 85 °C for drying and heat preservation for 3 h, and it is obtained after completion.

[0075] Comparative Example 5

[0076] The specific implementation manner of this comparative example is basically the same as that of Example 1, except that the preparation method of the modified resin includes the following steps: S1: Add 12.5 parts of acrylonitrile, 0.5 part of glycidyl acrylate and 1.2 parts of methyl methacrylate to 60 parts of acryloyl chloride solution, introduce nitrogen, add 0.12 part of potassium persulfate, and heat to 85 °C for reaction to generate a prepolymer; S2: Mix 12.5 parts of the prepolymer, 38.5 parts of acrylamide, 200 parts of deionized water and 0.22 part of potassium persulfate, and after the reaction system gas is fully replaced with nitrogen, react for 7.5 h to obtain a modified product solution; S3: Add ammonia water to the modified product solution to adjust the pH to 8.5, and naturally cool down, then add acetone for cyclic washing 3 times, and dry to obtain.

[0077] Comparative Example 6

[0078] The specific implementation manner of this comparative example is basically the same as that of Example 1, except that the preparation method of the modified resin includes the following steps: S1: Add 7.5 parts of acrylonitrile, 1.2 parts of glycidyl acrylate and 2.5 parts of methyl methacrylate to 60 parts of acryloyl chloride solution, introduce nitrogen, add 0.12 part of potassium persulfate, and heat to 85 °C for reaction to generate a prepolymer; S2: Mix 5.5 parts of the prepolymer, 45.5 parts of acrylamide, 240 parts of deionized water and 0.24 part of potassium persulfate, and after the reaction system gas is fully replaced with nitrogen, react for 7.5 h to obtain a modified product solution; S3: Add ammonia water to the modified product solution to adjust the pH to 8.5, and naturally cool down, then add acetone for cyclic washing 3 times, and dry to obtain.

[0079] Comparative Example 7

[0080] The specific implementation manner of this comparative example is basically the same as that of Example 1, except that the preparation method of the modified resin includes the following steps: S1: Add 7.5 parts of ethyl acrylate, 1.2 parts of dodecyl acrylate and 2.5 parts of 2-hydroxyethyl acrylate to 60 parts of acryloyl chloride solution, introduce nitrogen, add 0.12 part of potassium persulfate, and heat to 85 °C for reaction to generate a prepolymer; S2: Mix 12.5 parts of the prepolymer, 38.5 parts of acrylamide, 200 parts of deionized water and 0.22 part of potassium persulfate, and after the reaction system gas is fully replaced with nitrogen, react for 7.5 h to obtain a modified product solution; S3: Add ammonia water to the modified product solution to adjust the pH to 8.5, and naturally cool down, then add acetone for cyclic washing 3 times, and dry to obtain.

[0081] Performance evaluation

[0082] Anti-seepage pressure: Referring to the standard GB / T 50082-2009, the anti-seepage pressure test was carried out on the cementitious materials prepared in the examples and comparative examples. The results were expressed as the maximum non-seepage pressure, and the test values were the average of 10 tests and recorded in Table 1.

[0083] Compressive strength: Referring to the standard GB / T 50081-2019, the mechanical strength test was carried out on the cementitious materials prepared in the examples and comparative examples. The test values were the average of 10 tests and recorded in Table 1.

[0084] Anti-corrosion performance: Referring to JC / T 1011-2006, the 28d expansion rate test was carried out on the cementitious materials prepared in the examples and comparative examples. The measured values were the average of 10 tests and recorded in Table 1.

[0085] Table 1 Performance test results

[0086]

[0087]

[0088] It can be seen from the data results of the examples, comparative examples and Table 1 of this application that Examples 1 and 2 of this application have obvious advantages over Comparative Examples 1-7 in terms of strength performance, waterproof performance and anti-shrinkage performance, etc. This is mainly because of the combined effect of the modified gypsum, modified resin and other matching technical solutions limited in this application. However, since Comparative Examples 1-7 did not adopt the technical solutions limited in this application, obvious disadvantages appeared in the above performance tests, which further proves the necessity of the technical solutions limited in this application for the technical effects and solving technical problems of this application.

Claims

1. An ultrafine cement-based composite cementing material for underground mine filling, characterized in that: The raw materials are: 50-70 parts of ultrafine cement, 20-30 parts of tailings sand, 10-15 parts of modified desulfurized gypsum, 5-12 parts of fly ash, 8-16 parts of modified resin, 0.5-1.5 parts of reinforcing agent, 0.4-1.2 parts of water reducing agent, 5-15 parts of fiber material, and 40-60 parts of water. The average particle size of the ultrafine cement is 5-15 μm; The average particle size of the tailings sand is 0.5-1.5 mm; The fly ash is Class I fly ash or Class II fly ash; Preparation method of modified desulfurized gypsum The following steps are involved: S1: Add desulfurized gypsum to deionized water, add titanate coupling agent and polyvinyl alcohol and stir to mix evenly; S2: Add ammonia water, pullulan and silica sol to the reaction solution, heat to 70-75℃, and keep warm for 2-2.5h; S3: After the reaction is completed, add urea to the reaction solution and continue stirring for 100-120min; S4: After the stirring is completed, the product is filtered and placed in a ventilated oven for drying at 80-90°C for 2-3 hours. The mass ratio of the desulfurized gypsum, titanate coupling agent and polyvinyl alcohol is (8-10): (0.5-1): (1.6-2.2); The mass ratio of the desulfurized gypsum, amylopectin and silica sol is (8-10): (1-1.4): (0.5-0.8); The amount of urea added is 2.5-5wt% of the total mass of the reaction solution; Preparation method of the modified resin The following steps are involved: S1: Add acrylonitrile, glycidyl acrylate and methyl methacrylate to acryloyl chloride solution, introduce nitrogen, add potassium persulfate, heat to 80-90°C and react to generate a prepolymer; S2: prepolymer, acrylamide, deionized water and potassium persulfate are mixed, and after nitrogen fully replaces the reaction system gas, the reaction is carried out for 6-8 hours to obtain a modified product solution; S3: ammonia water is added to the modified product solution to adjust the pH to 8-8.5, and the temperature is naturally lowered, and then acetone is added to wash 2-3 times in a cycle, and then dried to obtain the modified product solution; The mass ratio of acrylonitrile, glycidyl acrylate and methyl methacrylate is (6-8): (1-1.5): (2-3); The mass ratio of the prepolymer to acrylamide is (10-15): (35-40).

2. The ultrafine cement-based composite binder material for underground mine filling according to claim 1, characterized in that: The mass ratio of the ultrafine cement, tailings sand, fly ash and fiber material is (55-65): (22-26): (8-12): (6-12).

3. The ultrafine cement-based composite cementing material for underground mine filling according to claim 2, characterized in that: The mass ratio of the ultrafine cement, modified desulfurized gypsum and modified resin is (55-65): (11-14): (10-15).

4. The ultrafine cement-based composite cementing material for underground mine filling according to claim 3 is characterized in that: The mass ratio of the prepolymer to acrylamide is (10-15): (35-40).

5. The ultrafine cement-based composite cementing material for underground mine filling according to claim 4, characterized in that: The enhancer is a combination of triethanolamine and calcium chloride.

6. The ultrafine cement-based composite cementing material for underground mine filling according to claim 5, characterized in that: The mass ratio of triethanolamine to calcium chloride is (1.5-2):(2.5-3.5).

7. The ultrafine cement-based composite cementing material for underground mine filling according to claim 6, characterized in that: The water reducer is at least one of polycarboxylic acid water reducers.

8. The ultrafine cement-based composite cementing material for underground mine filling according to claim 7, characterized in that: The fiber material is at least one of carbon fiber, glass fiber, polypropylene fiber, nylon fiber and stainless steel fiber.

9. A method for preparing an ultrafine cement-based composite binder material for underground mine filling according to any one of claims 1 to 8, characterized in that: The specific steps include: S1: After weighing the ultrafine cement, tailings sand, modified desulfurized gypsum, fly ash and modified resin in proportion, add them into a mixer for dry mixing for 3-5 minutes to ensure that the components are evenly distributed to obtain a dry mix; S2: Mix the reinforcing agent, water reducing agent, fiber material and water to obtain a mixed solution, mix the dry mixed material and the mixed solution until the slurry is uniform and free of lumps; S3: Fill and cure the obtained slurry for 28 days, and the slurry is obtained after completion.

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